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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 12 |
| 3 | 75 |
| 4 | 633 |
| 5 | 6330 |
| 6 | 70410 |
| 7 | 845490 |
| 8 | 10778385 |
| 9 | 144342129 |
| 10 | 2016502329 |
| 11 | 29249703273 |
| 12 | 439097183598 |
| 13 | 6807064047249 |
| 14 | 108811265375748 |
| 15 | 1791748638013341 |
| 16 | 30373586425246566 |
| 17 | 529855701281428431 |
| 18 | 9509268033398381151 |
| 19 | 175539561089425403601 |
| 20 | 3332349856995500161920 |
| 21 | 65037265540406292591147 |
[1,3,12,75,633,6330,70410,845490,10778385, 144342129,2016502329,29249703273,439097183598, 6807064047249,108811265375748,1791748638013341, 30373586425246566,529855701281428431, 9509268033398381151,175539561089425403601, 3332349856995500161920,65037265540406292591147] |